Grandma's Cheesy Potato Casserole

• * In a skillet, brown 1-chopped onion in a little olive oil. Set aside.
• Melt 1 - stick butter in a large mixing bowl in microwave.
• Add 2-lbs. Ore Ida O'Brian potatoes (1 1/2 bags) that have been thawed.
• Mix in 1 - can cream of chicken soup,  2-cups sour cream, 3 - cups shredded cheddar cheese and the onions. Stir to combine. 
• Pour into a casserole dish (9X13 will work). 
• Bake at 375 degrees F. for 1 hr. 15 minutes. 
• Serve.